Hello everybody,
I would like to make a question about the UV-VIS spectrum of silver nanoparticles. I started a project to synthesize silver nanoparticles in the plant extracts and I have two peaks in my spectrum, one narrow at 300nm and another wide at 400 nm. What I understood in some comments is that the peak at 300 nm is because of the silver that didn´t react and the peak at 400 nm is because of the silver nanoparticles so, my question is: Should the peak at 300 nm decrease with the time and the peak at 400 nm increase? Moreover, What does it mean to have a wide peak at 400 nm and a narrow peak at 300 nm?
Hi María Iglesias
in our data there is single pink at 400nm which can be attributed to teh surface plasmon resonance of the silver nanoparticles.
I think the peak at 300 nm is due to plant extract (organic moiety) first you have to standardize the ratio of plant extract and AgNO3 in such as way a that there is no peak below 400 nm. Try to reduce the plant extract volume and increase the volume of AgNO3. Further if you use less plant extract the synthesized silver nanoparticles will be of good quality.
Thank you for your answers. I will play a bit with the voulme of the extract and the concentration and volume of the AgNO3 solution.
A broad peak centered around 400 nm is the characteristic surface plasmon resonance absorption of spherical Ag NPs (Colloid. Surf. B. 113 (2014) 115-1240). The broadness of the band is due to the wide sizes of the nanoparticles. This is the only band expected for Ag NPs and the peak you observed at 300 nm must be coming from other species. Therefore, I think, if you wash the Ag NPs thoroughly with water and then with an organic solvent you will get rid of the unreacted Ag+ and the plant extract.
Hi,
According to Mie scattering theory SPR(Surface Plasmon Resonance) band for Silver nanoparticles is 380-420 nm. The peak within this region confirms the formation of Silver nanoparticles. out of this range there is no silver nanoparticles formed. So i think in your case silver nanoparticles were not yet formed . Increase the concentration of Plant extract and keep silver precursor concentration constant or increase the conc. of silver precursor and run the spectra. Pls check that other than reducing agent ,silver precursor other reagents absorption maxi ma for ex. stabilizing agent.
Best.
Thanks
All researchers are right. Peak at about 400 nm is related to metallic silver nanostructures. Peaks in the region of 280 (sometimes lower) - 330 nm are due to presence of ionic silver (including charged clusters). For the last one I have recommend few sources:
J. Am. Chem. Soc. 1990,112,46574664
J. Phys. Chem. 1993,97, 339-343
J. Phys. Chem. 1993,97, 4589-4594
Best regards
Thank you for your answers. I will try different concentrations of reductor agent and extract.
Kind regards
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